Optical powder spreadability sensor and methods for powder-based additive manufacturing

Abstract

Disclosed is an apparatus for and method of determining spreading behavior of a powder material during an additive manufacturing process. The method deposits a powder mound, moves a spreader to distribute a layer of powder over a build supported on a build area, operates an energy source to cast intercept the powder mound in the path of the source and onto an optical sensor during displacement of the powder mound, and analyzes an output of the optical sensor to identify features relating to the spreading behavior of the powder.

The invention claimed is: 
     
       1. An additive manufacturing apparatus comprising:
 a build platform arranged to support a build; 
 a table arranged that receives a deposited powder and a spreader that displaces the deposited powder to distribute a powder layer over at least the build platform, the spreader pushing an accumulation of powder in a mound across the table; 
 an optical sensor arranged in line with a light source, wherein the light source generates a light beam having a radial cross-section presenting a beam area of beam exposure that encompasses at least some of the mound of powder so as to cast a shadow having a shadow area of the powder mound onto the optical sensor for detection during displacement of the powder mound, wherein the light source and optical sensor are arranged at opposite ends of the spreader; and 
 an analysis unit that analyzes an output of the optical sensor to determine the spreading behavior of the powder based upon the shadow area detected. 
 
     
     
       2. The additive manufacturing apparatus according to  claim 1 , wherein the light source comprises a laser light source. 
     
     
       3. A sensor for use in additive manufacture apparatus having a build area, wherein a powder material is applied in successive layers using a spreader device extending across and moving along a surface of the build area in operation of the additive manufacture apparatus to deposit and smooth a layer of material, the spreader device pushing an accumulation of powder in a mound across the table, the sensor comprising:
 a source of radiant energy carried on the spreader device and generating, a light beam having a radial cross-section presenting a beam area of beam exposure that encompasses at least some of the mound of powder so as to cast a shadow having a shadow area; 
 a detector carried on the spreader device and spaced from and arranged to receive the energy beam, wherein the detector is spaced from the beam at a distance to span a width of the layer in an x-y plane and located such that a height of the material in the mound being applied and moved by the spreader device in a z axis orthogonal to the x-y plane will block at least part of the beam, and wherein the detector generates a signal that varies with the amount of beam blockage; and 
 an output generating device receiving the signal and providing an output correlated to the spreadability of the layer being applied. 
 
     
     
       4. The sensor of  claim 3 , wherein the source of radiant energy is a light source. 
     
     
       5. The sensor of  claim 4 , wherein the source of radiant energy is a laser. 
     
     
       6. The sensor of  claim 3 , wherein the spreader is an elongated blade, and wherein the radiant energy source is carried on a bottom end of the blade, and the detector is carried on an opposite end of the blade. 
     
     
       7. An additive manufacture machine using layerwise build-up to create an object, comprising:
 a build area, wherein a powder material is applied in successive layers; 
 a source of fluent build material; 
 an applicator device that moves across the build area and spreads the material in a first layer and then successive layers, the applicator device pushing an accumulation of powder in a mound across the build area; 
 a sensor array carried on the applicator device and generating a beam of radiant energy spanning a width across a layer being applied, wherein the array includes a beam generator and a beam detector, wherein the beam detector is arranged such that a layer being applied will intercept at least a part of the beam, 
 the beam having a radial cross-section presenting a beam area of beam exposure that encompasses at least some of the mound of powder so as to cast a shadow having a shadow area of the powder mound onto the beam detector, the beam detector being spaced from the beam at a distance to span a width of the layer, 
 the beam detector generating a signal that varies with the amount of beam blockage; and 
 an output generating device receiving the signal and providing an output correlated to the spreadability of the layer being applied.